Hi @akirkby249
You mention changing user name, the Application goes by your online account. Try clearing your cookies on your PC and try logging into your online account with your new user name and password, if this works there shouldn't be an issue with the Application.
Make sure you have the latest version of the Application installed by going into Applications > App details in store and checking for any update. You would already been into storage and cleared the App data and cache. After clearing details, in order for Vodafone to locate the account, you will need to use mobile data for the first log in.
You don't mention if you are a new customer or have previously been able to access the application, when you are a new customer, before being able to views usage you would need to wait until you are out of the pro rata billing period and have some online billing information.
If there are persistent problems, you have live chat, Customer Services or the Social Team for help and advise here Contact Us
